Motor control



A g- 5, 1947- G. c. ELLERBECK 2,425,178

MOTOR CONTROL Filed Nov. 27, 1943 F113 :3 7 BY 4 a ATTORNEY.

INVENTbR.

Patented Aug. 5, 1947 O UNITED STATESNIPATENT OFFICE 'Y imam I Moron corrmol.

Grant 0. Ellerbeck, San Leandro, Calif., assignor to Friden Calculating Machine 00., Inc., a corporation of California Application November 21, 1943, Serial No. 512,024

1 Claim. 1

This invention relates to electric motors and particularly to means for controlling the speed thereof.

The object of theinvention is to provide a device for controlling the speed of an electric motor which is responsive to air pressure.

In the drawings:

Fig. 1 illustrates an apparatus for demonstrating the principle of operation.

Fig. 2 is a sectional view of an electric motor in which my invention has been embodied.

Fig. 3 is a detail view taken as indicated by the line 3-3 in Figure 2.

Referring to Figure 1, the motor H1 is provided 'with a fan II which is secured to the armature shaft. 'Mounted on a block of insulation l2 are brackets l3, H in which a shaft I5 is slidably supported for axial movement. At the end adjacent the fan, the shaft I! has secured thereto a 'disc l6 which is subjected to air pressure from the fan II, this pressure varying in accordance with the speed of rotation of the fan.

The air pressure tends to move the disc l6 toward the left, and this movement is opposed by a leaf spring I! secured to a block 18 mounted on the block of insulation l2. The pressure exerted on the disc l6 by the spring I! can be adjusted by means of the screw H which is threaded into the bracket l3. The right end of the shaft i5 carries a contact point 20 adapted to cooperate with the contact point 2| supported by a bracket 22. A binding post 23 is provided on the bracket 22 for connecting a wire 24 in the motor circuit and similarly a wire 25 can be connected to the binding post 26.

In operation, when the motor is idle or running slowly, the spring I! maintains the contact 20 in engagement with the contact 2| so that the motor circuit is established. Upon an increase of speed of the motor, the pressure exerted b the fan on the disc 16 increasesuntil this pressure overcomes the counteracting pressure of the spring 11 and, at the pre-determined speed for which the apparatus is set removes the contact 2|! from engagement with the contact 2| thereby opening the motor circuit. Consequent reduction in the speed 01' the motor results in reduced air pressure on the disc l6 whereupon the spring l1 again closes the contacts. In this way by adjusting the screw IS, the apparatus can be mad to serve as a governor to maintain the motor at constant speed. The apparatus can also be employed for changing the speed of the motor by turning the screw l9. This use would be particularly adaptable when applied to an electric fan.

Figure 2 shows a motor of well-known construction, comprising an armature 36 on a shaft 3| joumalled in a casing 32. A fan 33 is mounted on the armature shaft for ventilating the motor.

2 a The xhaust from this fan is directed as indicated by the arrow 34 against a disc 35 mounted on a leaf spring 36 secured at its lower end at 31 to the casing 32. The pressure of the spring 36 may be adjusted by means of the screw 38 which is threaded into the casing 32. At the until the pressure of the spring 36 is overcome and the contact 40 is removed from contact ll. These contacts are connected in the motor cirout by means not shown.

In order to control the discharge of air against the disc 35, a perforated plate 42 maybe secured over a discharge outlet 43. A second perforated plate 44 is adjustably secured to the inner plate 42. By rotating the plate 44 (Fig. 3) relative .to the plate 42, the effectiveness-sectional area of the discharge outlet may b adjusted, thereby increasing or decreasing the air pressure exerted against the disc 35.

In order to adjust the governor, the disc 44 may be adjusted to vary the air pressure or the screw 33 may be adjusted to vary the spring pressure or both. In any event it will be evident that the device can be so adjusted that upon increase in motor speed to a pre-determined point, suincient air pressure is exerted against the disc 35 to open the contacts and that upon subsequent decrease in motor speed, the spring 36 will close the contacts.

Iclaim:

A governor for an electric motor provided with a ventilating fan, a leaf spring having means thereon to provide a surface subject to the pressure of air from said fan, said spring tending to oppose said air pressure, electric contacts in the motor circuit, movement .of said spring serving to open and close said contacts to govern the speed of said motor in accordance with air Dressure exerted by said ventilating fan, and an adjustabl outlet in the casing of the motor to varythe effective air pressure on the governor.

GRANT C. ELLERBECK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

